Generally, polyolefin resins such as polypropylenes, polyethylenes, ethylene-propylene copolymers, ethylene-propylene-diene copolymers, poly-4-methyl-1-pentenes, etc. are relatively inexpensive and have excellent performance in terms of, for example, chemical resistance, water resistance, heat resistance, etc. Therefore, polyolefin resins are used in a wide variety of applications such as raw materials for automotive parts, electronic parts, building materials, packaging films, and the like. However, since polyolefin resins are crystalline and non-polar, it is difficult to coat or bond polyolefin resins.
To coat or bond such low-adhesion polyolefin resins, chlorinated polyolefins having strong adhesion to polyolefin resins have been used as binder resins (JP 59-75958 A and JP 60-99138 A). Further, acrylic, urethane and/or polyester resins have been mixed or graft-polymerized with chlorinated polyolefins to obtain binder compositions for coating or bonding polyolefin resins, thereby compensating for the drawbacks of chlorinated polyolefins (JP 6-16746 A and JP 8-12913 A).
However, such binder compositions are mostly used in the form of solutions in organic solvents such as toluene, xylene, etc., and large amounts of organic solvents are released into the atmosphere during application of such compositions. Thus, such binder compositions are unfavorable from the viewpoint of the environment and health. Further, such binder compositions, which contain chlorine atoms, are also unfavorable from the viewpoint of toxic substance generation accompanying incineration.
Aqueous resin compositions which are organic solvent-free and whose resins contain no chlorine have been proposed (JP 6-256592 A and JP 2004-107539 A). However, such compositions have a problem in that emulsification steps in their production processes sometimes involve solvent removal that requires a long period of time, resulting in high cost. Moreover, polyolefin resins intrinsically have low polarity, and thus, when mixed with acrylic, urethane, epoxy and/or polyester resins, such polyolefin resins do not exhibit the desired properties due to low compatibility with these resins.